Blowpipe



W. J. JACOBSSON BLOWPIPE Filed April 17. 1957 April 23, 1940.

- INVENTOR WILGGT J. JACOBSSON ATTORNEY "lnllflllllll,

`Patented Apr. 23, 1940 UNITED STATES PATENT OFFICE BLOWPIPE of West Virginia Application April 17,

13 Clair-ns.

'I'his invention relates to ablowpipe, and more particularly to a blow pipe which is adapted to use medium pressure fuel gas eiilciently and Withrate at which the gas mixture leaves the blowpipe tip always exceeds the rate of propagation of the flame, flashbacks will notd occur. It is accordingly important to maintain a rate of mixed gas travel at the blowpipe tip which is greater than that of the name propagation. With fuel gas at moderate or low pressures and combustion-supporting gas at high pressure, it is customary to use the pressure of the combustionsupporting gas to aspirate the fuel gas, to effect the mixing, and also to impart to the mixture the necessary rate of travel. With fuel gas and combustion-supporting gas at more nearly the same pressure, aspiration, mixing, and mixture speed are not so effectively attained by means of the combustion-supporting gas pressure.

One object of the invention is therefore to provide a blowpipe wherein effective mixing and the required rate of mixture travel can be attained without aspirating one gas by means of the other. Another object is the provision of such a blowpipe which will be flashback-resistant. A further object is the provision of such a blowpipe in simple, rugged, and easily maintained form.

Other objects and novel features of the invention will be apparent from the following description takenvwith the accompanying drawing, in which:

Fig. 1 is a view partly in longitudinal section and partly in side elevation, showing a blowpipe constructed in accordance with the invention;

Fig, 2 is a cross section of the blowpipe taken on the line II-II of Fig. 1;

Fig. 3 is a fragmental plan view of the blowpipe as seenfrom the line III- III in Fig. 1; v

Fig. 4 is a cross section of a part of the blowpipe taken on the line IV-IV of Fig. l; and i Fig. 5'is a side elevation of the nozzle assembly cf the blowpipe.

According to the present inventioma blowpipe is provided having an improved preheat gas mixing assembly whereby flashbacks are prevented. The preheat gas mixing assembly includes a unitary nozzle assembly comprising a nozzle, an

1937, Serial No. 137,419

(Cl. 158-;Z7.4)

elongated conduit, and a rear block, all rigidly connected together in coaxial series alignment and disposed in an elongated cavity Within the blowpipe to provide a mixing gap, two concentric gas passages back of the nozzle and a metering constriction in each gas passage near the mixing gap. An especially designed mixing throat and expansion passage are also provided.

For convenience,v the words oxygen and acetylene" will be used in this specification to denote respectively any appropriate cutting and combustion-supporting gas and any appropriate fuel gas. The embodiment of the invention which is illustratedin the drawing shows a cutting blowpipe having inlet means for oxygen and acetylene and outlet means for a combustible mixture of oxygen and acetylene. The blowpipe comprises a head I-I and a valve block B, which are connected together by a cutting oxygen tube C, and by a combustible mixtureconduit M and an elongated tube 2|. Nipples O and A supply the valve block B with oxygen and acetylene respectively. A hollow nut N attaches the usual cutting tip T to the blowpipe head H in well-known manner.

Oxygen, entering the blowpipe through the nipple O, ows through a passage I0 to an annular valve chamber II. in the valve block B.

Passage of oxygen from the annular chamber II to the cutting oxygen tube C is regulated by a valve I2 which may be operated by any known Vor convenient valve operating construction: for instance, a lever-opened, spring-closed mechanism such as that illustrated. Passage of oxygen from the chamber II to the combustible mixture conduit M is regulated by a valve I3.

A duct I4 in the valve block B connects the annular chamber II with a valve chamber I5 in `which the valve I3 is operated by.a valve stem I8 and a handle I'I thereon. Combustion-supporting oxygen may accordingly be prevented from entering the valve chamber I5 by closing the valve I3 against the valve seat provided by the end of the ductl I4, whereas opening the valve I3 will permit combustion-supporting oxygen to enterthe valve chamber I5. A cross passage I8 connects the valve chamber I5 with a bore I9 Vin the valve block B ahead of an annular shoulder 20 therein, the purpose of which will be explained later.

The bore I9 extends completely through the valve block B and the opening therethrough continues forwardly through a tube or large conduit 2| which is gas-tightly connected to the valve block as by silver-soldering at 22. This conduit 'Ihe nozzle assembly7 X is c ncentrically disposed within the elongated cavi y. It comprises a nozzle 24, an elongated conduit 25, and a rear block 26, all rigidly connected together in coaxial series alignment and removably disposed in the.

velongated cavity. A longitudinal passage 21 extends substantially axially through the nozzle 24, and a longitudinal passage 28 extends substantially axially through the rear block 26, each passage being a continuation of the passage through the conduit 25. An annular shoulder 29, formed l on the rear block 26 ladjacent its forward end,

contacts the internal shoulder of the bore I9 and thereby limits the axial position ofthe unitary assembly within the elongated .cavity and also positions the nozzle 24 axially of the elongated cavity. Contact between the annular shoulders 20 and 29 seals 'the continuous passage through the nozzle assembly from the annular passage between the elongated conduit 25 and the elongated cavity ahead of the rear block 26 and prevents passage of gas from the elongated cavity on one side o'f the rear block to the other, except through the passage 28.

'I'he passage 28 through the rear block 26 is internally threaded in order that an instrument may be inserted therein for withdrawing the unitary-i assembly from the elongated cavity'. An ordinary long machine screw will serve for this purpose.

The nozzle 24 islong and may be substantially cylindrical in form, but is relatively short as compared to the lengths of the elongated cavity and the elongatedconduit 25. The major portion of its forward end yis a plane surface transverse to the axis of the nozzle. In the embodiment here particularly illustrated and described, the nozzle 24 has a plane forward end 30 standing substantially perpendicular to or at right angles to its axis. 'I'he passage 21 therethrough is long and may be constricted for a short distance, as at 3|, to provide a metering orifice. Although the nozzle 24 has a substantially uniform external diameter throughout most of its length, a series of radial projections 32 adjacent its forward end and a. second series' of radial projections 33 adjacent its rear end contact the inner wall of the large conduit 2| thereby spacing the nozzle with its external peripheral surface a uniform distance from the conduit and centering it'therein to provide a. continuous gas passage of substantially uniform cross-sectional area extending along the outside of and along the full length of said nozzle. The rear block 26 being designed to t exactly Within the bore I9, the entire nozzle assembly is thus accurately centered in the elongated cavity.

Since the nozzle assembly is positioned within the blowpipe by being slidably inserted into the elongated cavity from the rear, it is obvious that the bore I9 in the valve block B must be of a size to permit passage of the nozzle therethrough. It is also obvious that the reduction in diameter occasioned by the formation of the annular shoulder 20 in the bore I9 must be sufficient to prevent passage of the rear block 26.

The bore ls in the valve 'mock B is internally threaded at its rear end, and a locking screw 34 may be screwed into. .the bore to bear upon the rearface oi'- the rear block -26 and thus lock the unitary assembly in place. The locking screw has a central passage 35 therethrough resembling a keyhole, through which gas may pass to thev pas- `sage 2 8 in the rear block, and into which a tool may be inserted to turn the looking screw in the internal threads of the bore.

A threaded plug 36 having an external kerf in its head isscrewed into theend of the bore I9 :in the valve block B to close the bore. 'I'he length Jof the bore is such as to provide a space between the end of the threaded stem portion of the plug 'A36 and the locking screw 34 when both are in operative position. 'I'hus a chamber 31 is formed in the bore |9 between the locking screw and the plug.

The means including the cross passage I8 by which oxygen is conveyed 4to the annular passage lbetween the elongated conduit 25 and the large conduit 2| has already been described.

Acetylene, entering the blowpipethrough the nipple A, ows through an acetylene passage 38 in the valve block B to an acetylene valve chamber 39 in which a valve 40-on a'valve sternV 4I is oper- 'ated by a handle 42. Thevalve 40 controls passage of acetylene from the valve chamber 39- through a passage 43 leading therefrom to the I chamber 31 in the valve block. Thus, by' opening the valve 40 acetylene is free to flow from the valve chamber through the passage'43 into the chamber 31 and thence through the central passage in the locking screw 34, through the passage 28 in the -rear block, and through the elongated conduit 25 to the nozzle 24;

From the foregoing, it will be clear that, when the nozzle assembly X is in place and the threaded plug screwed into the end ofthe bore I9, there are two long concentric gas Supply passages in the blowpipe back of the mixing point. One com-A prises the chamber 31 and the axial passage through the nozzle assembly X, namely: the central passage 35 in the locking screw, the passage 28 in the rear block, the elongated conduit 25,

and the passage 21 in the nozzle, including the The other comprises thev the explosion wave due to the inertia of the large n volumes of gases in the gas supply passages, which resist passage backward through the valves, and hence act as pneumatic cushions to drive the backring gases forward again after extinguishment.

When. the nozzle 24 is in place, the plane face 30 at its forward or discharge end is spaced a very short distance from the rear end of the mixture conduit M which has a corresponding plane face 44`which also serves as the front face of a gap 45 which is thus formed between the parallel faces 3l) and". 'I'he Width of the gap 45 is quite small.

Tn some instances, it is only MM of an inch, or less. The gap '45 therefore forms a metering constriction in the oxygen line between the mixing point and the cushion in the oxygen supply line which is provided by the iarge volume oioxygen contained in the space between the large conduit 2l and the elongated conduit 25. r y

Under certain conditions it is founddesirable to provide the metering constriction in the oxygen supply line between the mixing point'andthe cushion by narrowing the clearance between the nozzle and the wall of the large conduit 2I'.' Such a constriction is illustrated at 45' and 'extends the entire length of the nozzle 24. The width of o the gap 45 need not then be so small, since the clearance `which'has just been described becomes the critical constriction. l

Passage of the proper quantities of acetylene and oxygen, respectively, to the blowpipe tip is assured by the metering orifice 3l in the nozzle, and by the metering constrictions 45 or 45', de. scribed above. With such properly proportioned metering constrictions, no greater volumes of gas` can be supplied to the blowpipe tip than the blowpipe is designed to burn emciently and without ashbacks. Although the pas/sages through and alongthe outside of the nozzle are constricted for gas measuring purposes, they are not constricted to such an extent as to prevent the free flow of gas and the free rearward passage of backpassage 41 to a tip cavity 50 in the head at a` point 5i therein from which the combustible gas mixture may pass conveniently through' thetip T. Thus the mixing throat 45 extends in continuation of the axial passage 21 in the nozzle; and its diameter may be substantially the same as that of the passage 21. Under certain conditions, it may be oi' advantage to make the diameter of the mixing throat 46 smaller or larger than that of the passage 21. The rear end of the mixing throat 46 may be flared or beveled, as indicated at 52, and is positioned directly opposite to the open end of the passage 21 in the nozzle 24.

Acetylene passing forwardly through the passage 21 is projected axially across the gap 45 toward the mixing throat. `At the same time oxygen passes inwardly of the gap, thus moving toward the column of acetylene at right angles thereto from all sides before the acetylene reaches the mixing throat. There is substantially no in jector action, but it is found that very effective mixing takes place when one gas moves through a narrow gap toward a column of the other gas at right angles thereto and on all sides thereof. Furthermore, it is not required that either gas be at a higher pressure than the other, and it is quite possible that both gases may mix effectively when they are at substantially the same pressure.

Blowpipes constructed in accordance with the invention produce an exceedingly` steady name. Should a backfire occur it will first enter the mixture conduit M, which is formed of a metal having high heat conductivity and which has exceedingly thick walls. The mixture conduit will therefore extract and dissipate much of the backfire heat quite rapidly. The danger that "this part may be damaged or burnt out is accordingly minimized. Next the backfire must the blowpipe again. When a backfire passes the metering constriction provided by gap 45' or space 45 and enters vthe voluminous annular oxygen chamber, the backflring gases are immediately burned in the large excess of oxygen and fail to become a flashback. Similarly, if any ybackiiring gas passes the metering constriction in the fuel gas line, it is smothered by the fuel gas in the elongated conduit 25.

The cutting oxygen valve I2 is made in conical form in order that it will necessarily open gradually and facilitate operation of the blowpipe in starting a cut.

From the foregoing, it will vbe apparent that a simple, rugged, and easily maintained blowpipe has been provided in which thorough mixing is effected without aspiration and in which flashback resistance is effectively maintained.

The form of the invention here described and illustrated in the accompanying drawing is disclosed merely to indicate how the invention may be applied. Other forms, differing in detail but not in principle from that here shown and described, will, of course, suggest themselves to those skilled in the art.

I claim:

1. In a medium pressure blowpipe, a mixture conduit having therein a mixing throat and a passage in continuation of the mixing throat, said mixture conduit having a plane surface perpendicular to the mixing throat at its rear end; a valve block having an opening therein;` and a tube gas-tightly sealed about the end of the mixing throat in said mixture conduit and about the end of the opening in said valve block, said tube having a combustion-supporting gas pas--V sage therein; in combination with a unitary assembly comprising a nozzle having a uniform external diameter throughout substantially its en, tire length, an elongated conduit, and a rear block, all rigidly connected together in coaxial series alignment, said nozzle and said rear block having fuel gas passages therethrough in continuation of the passage through said conduit, said nozzle also having a plane forward end disposed at right angles to the axis of the passage therethrough; means for spacing said nozzle from the end of the mixing throat; and means for spacing said conduit and said nozzle from said tube to provide two long gas chambers behnd the nozzle and to provide continuous gaspassage means of substantially uniform crosssectional area extending along the outside of and along the full length of said nozzle to permit the free passage of backres into the annular chamber surrounding said elongated conduit and within said tube.

2. A blowpipe having an elongated cavity therein forming a combustion-supporting gas passage and a combustible gas mixture passage ahead of said combustion-supporting gas passage, said mixture passage having a plane rear end substantially perpendicular to the axis thereof, in combination with an elongated conduit disposed substantially coaxially within the elongated cav- 'I5 ity forming a fuel gas passage, and a nozzle comprising a cylinder attachedvto the forward end of said A elongated conduit withinthe elongated cavity insaid blowpipe, said cylinder having a longitudinal passage therethrough in conl' tinuation of the passage through said elongated conduit, said cylinder also having a forward face substantially perpendicular to the passage there-l through and spaced from the rear end of said cylinder having a uniform external diameter throughout substantially its entire length.

y and the rear end of said mixture conduit in close` elongated conduit, and a rear block, all rigidly 3. In a blowpipe, in combination, a `valve block; a head; and a tip carried by said head; means providing an elongated gas passage interposed between said valve block and said head, a forward portionof said gas passage comprising a gas mixture conduit having therein an axial mixing throat and an axial expansion throat in con- "tinuation of said mixing throat, and a rear portion of said gas passage comprising a combustion-supporting gas conduit; a nozzle disposed within said elongated gas passage behind said mixing throat, said nozzle having a longitudinal fuel gas passage extending completely therethrough and a plane forward end disposed atright angles to the axis of said fuel gas passage,l said nozzle having a substantially uniform external diameter throughout its length, and the external wall of said nozzle being spaced from the internal wall of said elongated gas passage to permit the flow of gas along the outside of said nozzle, and the free passage of backres along the outside' of said nozzle into a backre extinguishing chamber in back of said nozzle; and means for spacing the forward end of said nozzle juxtaposition.

4. In a blowpipe including a tube; a nozzle having a uniform external diameter throughout substantially its entire length and having a longitudinal fuel gas passage therethrough and a plane forward end disposed at right angles to the axs of the longitudinal passage, the external peripheral surface of said nozzle and the internal wall of said tube being adapted to provide, when said nozzle isdisposed within said tube in spaced relation to the internal wall thereof, continuous combustion-supporting gas-passage means of substantially uniform cross-sectional area extending along the outside of and along the full lerigth of said nozzle whereby backilres may pass freely along the outside of said nozzle; in combination with a mixture conduit in spaced, coaxial relation with said nozzle, said mixture conduit havi'g therein a mixing throat and an expansion throat therebeyond.

5. For use with a blowpipe having an elongated cavity therein, a unitary assembly comprising a nozzle having'a uniform external diameter throughout substantially its entire length, an

connected together in coaxial series alignment, said nozzle and said rear block having longitudi- -nal passages therethrough in continuation of the portion of said gas conduit comprising a heavy walled combustible gas mixture conduit comprising a metal of high heat conductivity, and a rear portion of said gas passage being adapted to hold a large volume of combustion-supporting gas; a nozzle of less length than the rear portion 'of said gas conduit disposed therein to provide an elongated chamber in the rear thereof, said noz` zle having a uniform external diameter throughout substantially its entire length and being uniformly spaced from the internal wall of said gas condiut to provide a combustion-supporting gas passage along the outside of and along the full length of'said nozzle adapted to permit free pas- .sage of backfires into said chamber, and said,

nozzle having a longitudinal fuel gas passage therethrough and a plane front facejsubstantially perpendicular to said fuel gas passage spaced a predetermined distance from the rear end of said mixture conduit; means for supplying a fuelgas to said nozzle` passage; and means for supplying a combustion-'supporting gas to the rear portion of said elongated gas passage behind said nozzle.

7. A medium pressure blowpipe having an elongated cavity therein, in combinationwith a nozzle disposed in said cavity in uniformly spaced relation to the internal walls thereof, said nozzle having a substantially longitudinal passage therethrough and a 'plane front face substantially perpendicular to the axis of such passage, and having a uniform external diameter throughout substantially its entire length, said nozzle having a length less thanthe length of said caviity and being so disposed therein as to provide a voluminous chamber in the rear of said nozzle adapted to contain a volume of gas to extinguish 'backfires, and the space surrounding said nozzle between the external Wall thereof andthe internal wall of said cavity being adapted fto 'permit the free passage of backres therethrough; means for` supplying a Acombustion-supporting gas to said elongated cavity, said means being restricted relative to said cavity; and means for supplying a fuel gas to suc-h nozzle passage.

8. A blowpipe having an elongated cavity thereinforming. a combustion-supporting gas passage and a combustible gas mixture passage ahead of said combustion-supporting gas passage, said mixture passagehaving a plane rear end perpendicular to the axis thereof, in combination with a unitary assembly disposed in said cavity, said assembly comprising a nozzle, an elongated conduit, and a rear block, all rigidly connected together in coaxial series alignment, said nozzle and said rear block having fuel gas passages therethrough in continuation of the passage through said conduit, said nozzle having a plane front face substantially perpendicular to the passage therethrough spaced from the rear end Vof said mixture conduit to provide a mixing gap, said nozzle having a uniform external diameter throughout substantially its entire length, and

said nozzle having a length less than the length of said cavity and of said elongated conduit and being uniformly spaced from the internal wall of said cavity to permit the free passage of backiires along the outside of said nozzle, the space in the rear of said nozzle surrounding said elongated conduit and within said cavity, and the passage through said elongated conduit, being adapted to contain large volumes of gas to extinguish backfires.

9. In a blowpipe: the combination of a voluminous elongated oxygen conduit; a combustible gas mixture conduit ahead of said oxygen conduit; a nozzle having a uniform diameter throughout substantially its entire length disposed within said oxygen conduit, said nozzle having a fuel gas passage therethrough, and said nozzle `having radial projections adjoining each end thereof adapted to contact the inner wall of said oxygen conduit; said nozzle having a length less than the length of said oxygen conduit and being spaced from the internal wall thereof and from the rear end of said mixture conduit suiiiciently to permit the passage of a backfire along the outside of said nozzle, but being so disposed in said oxygen conduit as to provide a voluminous chamber in the rear of said nozzle adapted to contain a volume of oxygen for instantaneously completing the combustion of backring gases; means for supplying oxygen to said elongated oxygen conduit; and means for supplying a fuel gasto said nozzle passage.

10. In a blowpipe having a cavity, inlet means for oxygen and fuel gas, and discharge means for a combustible mixture of said oxygen and said fuel gas, the combination comprising a mixer nozzle having a uniform diameter throughout substantially its entire length disposed within said cavity in said blowpipe providing an oxygen conducting passage extending between the external periphery of said nozzle andl the inner wall of said cavity, said passage being adapted to permit backfires to pass freely therethrough the full length of said nozzle; means providing a passage for conducting fuel gas longitudinally through said nozzle; said blowpipe being provided With a mixing gap adjacent to the discharge end of said nozzle for receiving and mixing said oxygen and said fuel gas; and backfire extinguishing means comprising a large-volume chamber communicating with said oxygen conducting passage, said chamber being adapted to contain a Vrelatively large volume of oxygen to extinguish backiires which enter therein from said oxygen c-onducting passage.

11. In a medium pressure blowpipe having a cavity, inlet means for oxygen and fuel gas, and discharge means for a combustible mixture of said oxygen and said fuel gas, the combination comprising a mixer nozzle disposed within said cavity in said blowpipe, said nozzle having a discharge end and a fiat front face at said discharge end substantially perpendicular to the axis of said nozzle, and said nozzle having a uniform external diameter throughout substantially its entire length; means providing an oxygen conducting passage extending the full length of said nozzle between the external periphery thereof and the inner wall of said cavity, said passage beingadapted to permit backfires to enter freely therein; means providing a passage for conducting fuel gas longitudinally through said nozzle; a plurality of radial projections adjoining each end of said nozzle adapted to contact the inner wall of said cavity said blowpipe being provided with a mixing gap adjacent the discharge end of said nozzle for receiving and mixing said oxygen and said fuel gas, the front wall of said gap being substantially fiat and parallel to said nozzle front face; and backfire extinguishing means comprising a large volume chamber communicating with said oxygen conducting passage, said chamber being adapted to contain a relatively large volume of oxygen to extinguish backfires which enter therein from said oxygen conducting passage.

12. In a blowpipe: the combination of a voluminous combustion-supporting gas conduit; a combustible gas mixture conduit ahead of said combustion-supporting gas conduit and aligned therewith, the rear end of said mixture conduit comprising a plane surface perpendicular` to the longitudinal axis thereof; a mixing nozzle having a. uniform external diameter throughout substantially its entire length and having a longitudinal fuel gas passage therethrough, disposed in said combustion-supporting gas passage adjoining the forward end thereof, said nozzle having a plurality of radial projections on its periphery adjoining each end thereof contacting the internal Wall of said combustion-supporting gas conduit whereby the external surface of said nozzle and the internal wall of said combustionsupporting gas conduit are uniformly spaced from one another to provide a continuous free passage for the straight line iiow of backres along the outside of and along the full length of said noz zle, the forward end of said nozzle comprising a plane surface perpendicular to the longitudinal axis thereof and spaced slightly from the rear end of said mixture conduit to provide a mixing gap.

13. A blowpipe having a tubular cavity therein; a conduit in said cavity with its external wall spaced from the internal wall of saidcavity; a mixing nozzle carried by said conduit on the forward end thereof, the external side wall of said nozzle being uniformly spaced from the' internal wall of said cavity to provide a straight passage therebetween extending the full length of said nozzle, said nozzle having a passage therethrough in communication with said conduit; means for supplying combustion-supporting gas to the space between the external wall of said conduit and the internal wall of said cavity whereby such gas iiows straight past said nozzle the full length thereof without changing direction; means for supplying fuel gas to said conduit whereby such gas flows through said nozzle passage; said nozzle having a forward end comprising a plane surface perpendicular to the direction of flow of gas within and without said nozzle; and a combustible gas mixture conduit having a rear end comprising a plane surface 4free passage of backfires therethrough into the portion of said cavity behind said nozzle.

WILGOT J. JACOBSSON. 

